Spring 2000 Presentation Summary:

The unpredictability of Class III growth poses a difficult decision in borderline Class III cases: whether to treat surgically or non-surgically. Dr. McLaughlin presented the limits and options of dental compensations in a non-surgical treatment without jeopardizing the possible surgical option.

Four primary areas are identified in making a decision on non-surgical treatment. The vertical and horizontal components of the problem, the position of the incisors and the amount of crowding. A low-angle Class III case can be compensated for by opening the bite, but achieving an anterior overbite in a Class III high angle case will be more difficult. Removing bicuspids (to move the molars mesially) out of the wedge will not close the bite and there may even be some bite opening, as the molars may extrude as they are moved mesially. Extractions may not close the skeletal vertical dimension, but may allow enough tooth movement to have anterior contact.

Limits of Dental Compensation

In evaluating the horizontal component, most Class III cases show a mid-face retrusion rather than a mandibular prognathism, which would require surgery. Dental compensations can be used, if the mid-face retrusion is not too severe. The WITS analysis is used to establish limits to planned dental compensation of moving the upper anteriors 120° to the palatal plane and the lower anteriors 80° to the mandibular plane. If the upper anteriors start at 100° to the palatal plane and are moved 120° that means 14mm of extra space. (If 3° = 1mm then 20° = approximately 7mm. If the central incisor moves forward 7mm, that means 7mm of extra space on either side, therefore 7 x 2 = 14mm). The same can be applied to the lower arch if the lower incisors are moved from 100° to 80° to the mandibular plane.

Treatment/Extraction Options

In a Phase I treatment of a cooperative patient, Dr. McLaughlin will use a Delaire face mask off Class III hooks that are attached to a .045 buccal and lingual wire soldered to the upper first molar bands. With a semi-cooperative patient, he will use an upper and lower 2 x 4 appliance, so that Class III elastics can be worn during the day and the face mask at night. Some cases will need expansion with a hyrax first, to correct a cross bite or make space for crowding. The expansion should be held with a palatal bar. The anterior cross bite can be jumped in two to three months with good cooperation. Before discontinuing the face mask, his goal is a 4mm overjet. The Phase I change is primarily dento alveolar, although some cases experience a slight orthopedic effect. The Class III elastics may cause some downwards and backwards movement of the maxilla.

If a case has crowding, lower anterior stripping may provide a positive overjet or at least an edge-to-edge position. A lower lingual arch may be used to preserve the E space. Other cases may work with the removal of a lower anterior tooth or lower bicuspids. There is also the possibility of extracting upper 5’s and lower 4’s.

In a Class III case, when the upper is treated non-extraction with lower extractions, a Class III molar relationship will result that may need equilibration. Another concern is whether the upper second molar will have an opposing tooth for occlusion. It may be possible to extend the distal of the lower second molar with a filling to make contact with the upper second molar. This may be a better solution than extracting the upper second molar as well as all four third molars.

Dr. McLaughlin presented some cases with the removal of lower second molars, treating the upper arch non-extraction. This can help control the vertical dimension, but sometimes the upper second molar needs to be held from extruding with a heavy lingual wire bonded from 6 to 7. A posterior open bite sometimes results after the lower second molars are removed, possibly caused by a lateral tongue thrust. You may also see a narrowing of the upper arch, so consider a palate bar. Treatment of a Class III, with the removal of lower second molars, may show no changes in the palatal or mandibular plane, that is, no opening of the vertical. There may be some flattening of the mandibular plane with the use of Class III elastics. The future status of the third molars in these cases in not predictable. They may need to be uprighted later, or even removed. But both the patient family and family dentist should have adequate information about the choice of compensatory treatment over surgery. Loss or retention of the wisdom teeth is a secondary issue. He stressed the importance of telling patients that jaw surgery may still be an option in compensatory treatment as the growth variable is not predictable.

As is typical with his presentations, Dr. McLaughlin showed many cases with complete and well photographed "before" and "after" records demonstrating his lecture material.

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